A major hurdle to advances in treating cancer is the relative lack of agents that can selectively target the cancer while sparing normal tissue. For example, radiation therapy and surgery, which generally are localized treatments, can cause substantial damage to normal tissue in the treatment field, resulting in scarring and loss of normal tissue. Chemotherapy, in comparison, which generally is administered systemically, can cause substantial damage to organs such as the bone marrow, mucosae, skin and small intestine, which undergo rapid cell turnover and continuous cell division. As a result, undesirable side effects such as nausea, loss of hair and drop in blood cell count often occur when a cancer patient is treated intravenously with a chemotherapeutic drug. Such undesirable side effects can limit the amount of a drug that can be safely administered, thereby hampering survival rate and impacting the quality of patient life.
Regarding tissue injuries, substantive basic science and clinical research have been conducted to evaluate the mechanisms of wound healing, the efficacy of various modalities for treatment of wounds, and the best methods for diagnosing wound infection. A great deal of this effort has been directed toward evaluating the most accurate and reproducible methods for diagnosing chronic wound infection. Chronic wounds often harbor bacteria at levels many times that which constitute infection in an acute surgical wound; yet, many of these chronic wounds go on to closure despite very high levels of microorganisms. There are several intrinsic limitations to diagnosing a wound infection and establishing a treatment paradigm via clinical signs and symptoms alone. Of particular concern is the constantly evolving number of microorganisms with antibiotic resistance. While the evaluation of clinical signs and symptoms may prove to be a very cost-effective and expedient method for diagnosing chronic wound infection, the use of this method alone does not inform the wound care clinician of the most appropriate chemotherapeutic approach to treatment. Use of clinical signs and symptoms alone leaves the provider to select a therapeutic agent based on little specific information about the particular pathogen(s).
Thus, there is a need for new therapeutic strategies for selectively targeting tumors and wounds, and reducing the side effects associated with systemic therapy. The present invention satisfies this need by providing molecules that selectively home to tumors and tissue injuries, and which are suitable for selectively targeting chemotherapeutic drugs, gene therapy vectors or other agents to the appropriate tissue. Related advantages also are provided.